Why does .psf appear as a computer?

So sorry for the newbie question, but why does .psf appear as a computer under my Windows 7 Network? Can I remove it and do I need it? I would like my system configured so that my Windows 7 files are accessible in Leopard and vice versa but I don't want a special folder. I just want to give sharing permissions to the folders as I see fit.
Also, why doesn't my Windows 7 generate the Network map when you click "See full map" under Network and Sharing Center?

Thanks in advance.